I've also noticed this. I'm using the exact same guide data as I was when I was running DVBViewer (EPGCollector has simply been reconfigured to run as a DVBLogic Plugin instead of injecting into DVBViewer). A full import of guide data when using DVBViewer takes only a few seconds and you can barely read the channel names as they whiz through so quickly (~100 channels). But with DVBLink, each channel name appears for about 0.5s making for a very slow import. The "Importing guide from clients" dialogue has actually become quite an annoyance as it partially obscures the view of the wall view if you're looking for a movie or TV show to watch.

Is this a shortcoming of the Kodi addon or the actual DVBLink Server? Is there anyway this can be sped up?

7 days, that's all Sky supply when you pull the EPG data direct from the satellite. As I said, the amount of data and for which channels should be exactly the same, I didn't change my EPG Collector settings, simply switched from pumping the data into the DVBViewer Recording Service to acting as the DVBLogic EPG plugin. I always make sure to exclude any channels I'm not using in EPGCollector in order to keep the amount of data collected to a minimum. Unless you're aware of some difference in the way DVBLink utilises EPGCollector when used as a plugin?

If I view the guide in Kodi when using DVBiewer, I get the full 7 days for all channels. Just as I do with DVBLink, only difference is the amount of time it takes to import said data from the backend. I'm not sure how DVBViewer stores the EPG data once it's been received from EPGCollector. Maybe they store it in such a way that it can be accessed more quickly when a Kodi client asks for it? Or maybe their Kodi addon requests the data in a different way? Or maybe their service sends the data to Kodi in a more efficient manner?

edit: I'm just running some tests now, going to try and get Kodi debug logs to compare a DVBLink EPG import with a DVBViewer one, will take a few minutes.....

As you can see, DVBLink takes 45 seconds from the moment the EPG database is cleared in Kodi. DVBViewer is done in 4 seconds. Hopefully these logs disclose somehow how they are doing it so quick?

edit: I should probably mention, all this testing is being done using the Kodi client (Jarvis final) on the same machine that's hosting DVBLink/Viewer. This machine has an i7 5820k so may be doing some of this quicker than the little i3 NUCs can.